1. Field of the Invention
The present invention relates to a printing method for a printing press and a printing press, the method involving printing images on sheets of paper fed using ultraviolet curable paints, and irradiating the ultraviolet curable paints on the printed sheets fed with ultraviolet light from light emitting diodes so as to cure the paints. The “paints” as used herein include inks as well as varnishes for use in surface protection and gloss finishing of ink-printed materials.
2. Related Art
Printing presses that perform printing with ultraviolet curable inks have been used heretofore, and for curing the ultraviolet curable inks on the sheets of paper by mean of ultraviolet irradiation, there is proposed a printing press including a single ultraviolet lamp (e.g., a mercury lamp or a xenon lamp) of a size slightly longer than the width of a sheet-conveying cylinder (e.g., see Japanese Patent No. 2006-297690 (FIG. 5)).
The printing press sometimes performs printing on a sheet of a smaller width than the cylinder. As shown in FIG. 9, in order to cure the ultraviolet curable inks on a sheet P of a smaller width than a cylinder 3 while the sheet P is being conveyed, ultraviolet light is applied thereto from an ultraviolet lamp 200 located above the cylinder 3; in this case, the ultraviolet light is thrown also on exposed surfaces 3A and 3B on both lateral ends at the right and left of the cylinder 3, which leads to corrosion of the metallic cylinder 3, deterioration of accuracy in registration of the sheet P due to thermal expansion of the cylinder 3, and in addition, cure of some ultraviolet ink misted over the exposed surfaces 3A and 3B of the cylinder 3 and adhered thereto as a result of ultraviolet irradiation.
And besides, the aforementioned lamp not only is short in service life but also generates much heat and consumes much power. For this reason, a printing press adopting light emitting diodes capable of ultraviolet radiation has been proposed recently (e.g., see Japanese Unexamined Patent Publication No. 2005-238562 (FIG. 1)).
Although the configuration as disclosed in Japanese Unexamined Patent Publication No. 2005-238562 is advantageous in terms of service life, heat generation, and power consumption, the configuration still involves a problem as described above of corrosion of exposed portions in the case of applying ultraviolet light to a sheet of paper of a smaller width than a cylinder, which calls for further improvement.